Four National Guard helicopters just flew over Kirkwood, Missouri heading north towards Ferguson. This is definitely not normal.
It is common in Denver for military helicopters to fly low altitude in formation right over the center of the city, back and forth mostly SE -- NW directly over my apartment building close to the capitol. There were three in formation yesterday, whop whop whop whop, most annoying. Apparently they're training. (It was worst of all during the 2008 Democrat convention August 25-Aug 28. Goodness, Democrats have money and are not afraid to show it conspicuously. Continuous streams of helicopters, not just military, every helicopter in the area was put to use, as many as the air lanes could handle. Also entire fleets of stretched limousines filling the streets in steady streams. A visit by the Pope brings the same military helicopters, but minus the limousines.)
Clayton Missouri National Guard completes departure from Ferguson 8/27/2014
Colorado's Ft. Lupton's (I think) has these same helicopters.